The invention relates to fuel injection control apparatus and method for a directly injected fuel engine, and more particularly to control of fuel injection of an engine capable of switching between stratified combustion and homogeneous combustion and which provides a reduction in fuel when decelerating or the like, whereby the start of fuel injection from the condition in which the fuel is reduced is controlled.
In recent years, direct injection engines have been developed for use as automotive engines, a fuel injection valve that injects fuel such as gasoline directly into the combustion chamber being provided, wherein in the low-load and medium-load regions, by injecting fuel during the compression stroke, stratified combustion is achieved by generating a stratified combustible mixture only in the region of the spark plug, thereby enabling a great increase in the leanness of the air-fuel ratio, and providing a great improvement in fuel consumption and emissions performance. In this system, however, when the load exceeds a predetermined load, to achieve the desired torque with a limited cylinder volume, fuel is injected on the intake stroke, thereby forming a homogeneous air-fuel mixture for the performance of homogeneous combustion.
As a measure to improve fuel economy, in the decelerating condition, in which the throttle valve is fully closed with the engine speed at or above a predetermined speed, the injection of fuel into the engine has been cut in the past, in what has come to be known as the deceleration fuel-cutoff mode.